Breast cancer health centre

Hormonal therapy for breast cancer

Hormonal therapies may be recommended for certain types of breast cancer, and work by reducing oestrogen levels or preventing the hormone from promoting cancer cell growth.

Hormonal therapy for breast cancer overview

There are two types of hormone therapy for breast cancer.

• Drugs that inhibit oestrogen and progesterone from promoting breast cancer cell growth.
• Drugs or surgery to turn off the production of hormones by the ovaries.

Do not confuse the term hormone therapy that is used for treating breast cancer patients with hormone replacement therapy that is typically used by post- menopausal women. Hormone therapy for cancer treatment stops hormones from getting to cancer cells. Hormone therapy for post- menopausal women without cancer (hormone replacement therapy or HRT) adds more hormones to your body to counter the effects of loss of these hormones at the menopause.

Who gets hormone therapy for cancer?

As part of the diagnosis process, tests are done to determine if the cancer cells have oestrogen or progesterone receptors. If so, that means that growth of the cancer can be stimulated with these hormones. If a cancer is found to have these receptors, hormone therapy is recommended as part of the treatment plan.

What drugs are used?

There are several common hormone therapy drugs used for breast cancer:

• Tamoxifen
• Toremifene
• Anastrozole
• Exemestane
• Letrozole
• Goserelin

Tamoxifen

Tamoxifen is a pill that has been used for more than 20 years to treat breast cancer. Tamoxifen decreases the chance that some early-stage breast cancers will recur and can prevent the development of cancer in the unaffected breast. Tamoxifen also slows or stops the growth of cancer cells present in the body.

In addition, tamoxifen may offer an alternative to watchful waiting or prophylactic (preventative) mastectomy for women at high risk of developing breast cancer.

Tamoxifen is a type of drug called a selective oestrogen-receptor modulator (SERM). At the breast, it functions as an anti-oestrogen. Oestrogen promotes the growth of breast cancer cells and tamoxifen blocks oestrogen from attaching to oestrogen receptors on these cells. By doing this, it is believed that the growth of the breast cancer cells is stopped.

Women who should definitely not use tamoxifen include pregnant women, women planning to become pregnant, men or women with a history of blood clots or stroke, or those taking anticoagulants. Your doctor will advise whether tamoxifen is appropriate for you.

For women, the side effects of tamoxifen are similar to some of the symptoms of menopause. Two of the most common side effects are hot flushes and vaginal discharge. Other side effects in women may include:

• Vaginal dryness and/or itching
• Irregular menstrual periods
• Headache
• Nausea and/or vomiting
• Skin rash
• Fatigue
• Fluid retention and/or weight gain

While some of its side effects are similar to menopausal symptoms, tamoxifen does not cause a woman to begin menopause.

Side effects in men may include:

• Headache
• Nausea and/or vomiting
• Skin rash
• Sexual side effects: impotence or decrease in sexual interest